To a soldier in a foreign, hostile city, the crack of sniper fire can be as confusing as it is terrifying. The walls and corners of buildings and tunnel-like city streets can reflect, bend, and channel sound waves, making it impossible to identify their point of origin—for a person, at least. An experimental new computer program can track echoing sound right back to its source.

Lanbo Liu and Don Alberts, geophysicists with the U.S. Army’s Cold Regions Research and Engineering Laboratory in Hanover, New Hampshire, placed a series of microphones throughout a full-scale military training village containing one- and two-story concrete buildings. When a sniper fired a shot into the city, the sensors recorded the sounds and relayed the information to a computer containing a digital replica of the city. The computer then created a time-reversed version of the sound waves that struck each sensor, zeroing in on the place where they all converged: the location of the sniper.

The system should work in any urban environment that can be outfitted with sound detectors and premapped into a computer. In fact, complex urban areas (central Baghdad or New York City, for instance) generate more sound paths and therefore could yield more accurate results. Moving objects, such as cars, complicate the analysis, however. “Currently, it takes hours to process the data. We’ll need faster algorithms and bigger computers to do it in real time,” Liu says. He expects to have a field-ready model within a few years.

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Jonathan

September 16, 2004, 06:13 PM

If you search around, you can find more information on this subject.

There are some really cool forward and reverse sound wave models in color video format that illustrate really well what's going on.

I've got some copies stored locally on my computer: if anyone is really interested, I'll email them or upload to a host, if anyone can find one.

Michigander

September 16, 2004, 06:19 PM

The actual magazine article had a color picture of a computer model of a gun shot in a mock city with various size buildings arranged at various angles and spacing. I was hoping the online version had it too, but it doesn't.

Jonathan, maybe you could post one as an example. I thought it was pretty interesting.

2nd Amendment

September 16, 2004, 06:43 PM

They were talking about a version of this 8 or ten years ago. When deployed it was...ummm...much less effective than expected. My money will continue to remain on the sniper.

MrMurphy

September 16, 2004, 06:57 PM

Not to mention suppressed rifles and immediate sniper displacement.

lbmii

September 16, 2004, 08:10 PM

Is Chicago using this system?

possenti

September 16, 2004, 09:31 PM

I've heard about this technology for a few years, and it always struck me as odd that there was no mention of using it during the "Beltway Sniper" incident. Maybe there was...

Maybe I missed the news reports, but NO ONE in law enforcement that I saw interviewed even brought the subject up. Did anyone hear anything?

Maybe my tinfoil needs to be polished, but I was under the impression that the powers-that-be wanted to prolong the terror in order to push an agenda. As many predicted, the perp(s) were caught by common citizens.

NukemJim

September 17, 2004, 07:44 AM

Is Chicago using this system?

Chicago is using a system but from the description I do not think it is the same one.

Newspaper articles did not give all of the details on the current system.

However they did state that in order to reduce the number of false alarms the system that Chicago uses does not work off of the sound of the muzzle blast. It works of the "sonic boom" of the bullet which is produced by the bullet which is travelling faster than the speed of sound.

I guess nobody told them that not all bullets are supersonic.

That is okay, after all there are no guns in Chicago. It is against the law.

NukemJim

Bubbles

September 17, 2004, 09:14 AM

My husband and I took an urban sniper class last year. A bit was covered about how sound reflects off of buildings, mountains, etc. and how in warfare situations a good sniper can use his knowledge in this area to further mask his location.

A suppressed rifle with subsonic ammunition would also foil such a system. I've got a Remington 700 in .308 and an AWC suppressor for it. With subsonic hand-loads it's a great rifle for "suburban whitetail" for those transition zones where housing developments are being built next to farms. The new residents don't hear a thing. :D

Jonathan

September 17, 2004, 01:03 PM

Well, another forum saw this one, and someone there had the original links.

http://www.acoustics.org/press/147th/liu-albert.html

http://www.aip.org/pnu/2004/split/687-1.html

Modeling the sound in the forward direction:
http://www.acoustics.org/press/147th/Color_echos_r.jpg (http://www.acoustics.org/press/147th/forward_model_CRREL.avi)

Modeling in reverse from the sensors to determine the source:
http://www.acoustics.org/press/147th/forward_model_run_r.jpg (http://www.acoustics.org/press/147th/time_reversal_method_CRREL.avi)

Zundfolge

September 17, 2004, 01:18 PM

Chicago is using (or is going to use ... not sure its in place yet) a system thats not quite as advanced as this. It won't plot trajectories, but will identify a "gunshot" and pinpoint the source

http://www.futurepundit.com/archives/002039.html

I believe this is the system in Chicago http://www.bbn.com/boomerang/index.html

igor

September 17, 2004, 07:31 PM

The system should work in any urban environment that can be outfitted with sound detectors and premapped into a computer.

Sounds just like your average urban warfare environment... why not outfit the battle field with soft ambient lighting, comfy sofas and a sound system oozing smooth jazz for everybody to just hang loose and forget about all this waging a war stuff to, while at it?

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